NHLBI recently approved and funded a multicenter secondary intervention trial to test the efficacy of propranolol in promoting longevity in patients suffering an acute myocardial infarction. This "Beta-blocker Heart Attack Trial" involves 32 geographically dispersed centers that are in the process of recruiting approximately 4,200 subjects over a two-year period with plans to follow these patients for an average of three years. The Rhode Island BHAT center is receiving sera obtained from each BHAT patient at the time of enrollment and at 6 and 12 months after infarction. These sera will be analyzed for their content of cholesterol, triglycerides, high-density lipoprotein (HDL)-cholesterol, and the major HDL protein, apolipoprotein A-I. A control population from a health maintenance organization in Rhode Island will be similarly tested. Data will be analyzed to determine the prevalence of lipoprotein abnormalities in victims of myocardial infarction, the independence of interrelatedness of these abnormalities, the effects of myocardial infarction on the observed levels of these quantities, and the effect, if any, of propranolol on their concentrations in sera. The ultimate aim will be to construct comprehensive lipoprotein profiles that will be useful in the identification of patients at coronary heart disease risk who are free of clinically apparent disease. Preliminary studies have already been performed on the sera of the first 530 patients enrolled and the first 67 subjects to return 6 months postinfarction for evaluation. They demonstrate striking peri-infarction changes in both total and HDL-cholesterol concentrations.